To ask the Secretary of State for Transport what the most recent estimate is of the percentage contribution of aviation, based on emissions by all aircraft departing from UK airports, and including the radiative forcing effect, to UK climate change emissions.

International aviation is not included in the UK's climate change inventory as there is no internationally agreed method for allocating such emissions among states. In 2005 aviation represented 6.3 per cent. of UK emissions, calculated as a proportion of emissions in the UK inventory plus emissions from international aviation and shipping departing the UK. Detailed data may be viewed at:

As the "Future of Air Transport Progress Report" (December 2006) noted, aviation emissions arising from the combustion of kerosene include carbon dioxide, water vapour, nitric oxide and nitrogen dioxide, particulates and other compounds. These give rise to "radiative forcing" impacts. The total radiative impacts were estimated by the EC TRADEOFF project to be approximately twice those of carbon dioxide (excluding cirrus cloud formation).

Using a radiative forcing multiplier of two, emissions from flights departing the UK contributed approximately 13 per cent. of total UK emissions in 2005. However, the figures for non-aviation sources do not include any radiative forcing attributable to them, as conclusive figures are not available.